Image generation in an electronic device using ultrasonic transducers

ABSTRACT

A method for generating an image is provided. The method comprises capturing a first set of image pixels by an ultrasonic sensor comprising an array of ultrasonic transducers using a first beamforming pattern, wherein the first beamforming pattern comprises a first pattern of transmit signals routed to a plurality of ultrasonic transducers of the ultrasonic sensor. The method further comprises capturing a second set of image pixels at the ultrasonic sensor using a second beamforming pattern, wherein the second beamforming pattern comprises a second pattern of transmit signals routed to the plurality of ultrasonic transducers. The second beamforming pattern is different than the first beamforming pattern. The second set of image pixels corresponds to an edge region of the ultrasonic sensor. The method additionally comprises combining the first set of image pixels and the second set of image pixels to form the image. An electronic device and a method of generating an image of a fingerprint with a fingerprint sensor are also provided.

RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S.patent application Ser. No. 15/611,704, filed on Jun. 1, 2017, entitled“IMAGE GENERATION IN AN ELECTRONIC DEVICE USING ULTRASONIC TRANSDUCERS,”by Garlepp, et al., having Attorney Docket No. IVS-743, and assigned tothe assignee of the present application, which is incorporated herein byreference in its entirety.

BACKGROUND

Piezoelectric materials facilitate conversion between mechanical energyand electrical energy. Moreover, a piezoelectric material can generatean electrical signal when subjected to mechanical stress, and canvibrate when subjected to an electrical voltage. Piezoelectric materialsare widely utilized in piezoelectric ultrasonic transducers to generateacoustic waves based on an actuation voltage applied to electrodes ofthe piezoelectric ultrasonic transducer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe Description of Embodiments, illustrate various embodiments of thesubject matter and, together with the Description of Embodiments, serveto explain principles of the subject matter discussed below. Unlessspecifically noted, the drawings referred to in this Brief Descriptionof Drawings should be understood as not being drawn to scale. Herein,like items are labeled with like item numbers.

FIG. 1A is a diagram illustrating a piezoelectric micromachinedultrasonic transducer (PMUT) device having a center pinned membrane,according to some embodiments.

FIG. 1B is a diagram illustrating a PMUT device having an unpinnedmembrane, according to some embodiments.

FIG. 2 is a diagram illustrating an example of membrane movement duringactivation of a PMUT device having a center pinned membrane, accordingto some embodiments.

FIG. 3 is a top view of the PMUT device of FIG. 1A, according to someembodiments.

FIG. 4 is a simulated map illustrating maximum vertical displacement ofthe membrane of the PMUT device shown in FIGS. 1A-3, according to someembodiments.

FIG. 5 is a top view of an example PMUT device having a ring shape,according to some embodiments.

FIG. 6 is a top view of an example PMUT device having a hexagonal shape,according to some embodiments.

FIG. 7 illustrates an example array of circular-shaped PMUT devices,according to some embodiments.

FIG. 8 illustrates an example array of square-shaped PMUT devices,according to some embodiments.

FIG. 9 illustrates an example array of hexagonal-shaped PMUT devices,according to some embodiments.

FIG. 10 illustrates an example pair of PMUT devices in a PMUT array,with each PMUT having differing electrode patterning, according to someembodiments.

FIGS. 11A, 11B, 11C, and 11D illustrate alternative examples of interiorsupport structures, according to various embodiments.

FIG. 12 illustrates a PMUT array used in an ultrasonic fingerprintsensing system, according to some embodiments.

FIG. 13 illustrates an integrated fingerprint sensor formed by waferbonding a CMOS logic wafer and a microelectromechanical (MEMS) waferdefining PMUT devices, according to some embodiments.

FIG. 14 illustrates an example ultrasonic transducer system with phasedelayed transmission, according to some embodiments.

FIG. 15 illustrates another example ultrasonic transducer system withphase delayed transmission, according to some embodiments.

FIG. 16 illustrates an example phase delay pattern for a 9×9 ultrasonictransducer block, according to some embodiments.

FIG. 17 illustrates another example phase delay pattern for a 9×9ultrasonic transducer block, according to some embodiments.

FIG. 18 illustrates a plan view of simulated ultrasonic pressure on thefocal plane for an example ultrasonic transducer system using threetiming phases, according to an embodiment.

FIG. 19 illustrates a cross section of simulated ultrasonic pressure onthe focal plane for an example ultrasonic transducer system using eitherthree or five timing phases, according to an embodiment.

FIGS. 20A-C illustrate example transmitter blocks and receiver blocksfor an array position in a two-dimensional array of ultrasonictransducers, according to some embodiments.

FIG. 21 illustrates an example ultrasonic transducer system with phasedelayed transmission, according to some embodiments.

FIG. 22 illustrates an example ultrasonic transducer system with phasedelayed transmission, according to some embodiments.

FIG. 23 illustrates an example ultrasonic transducer system with phasedelayed transmission, according to some embodiments.

FIGS. 24A and 24B illustrate example phase delay patterns for a 5×5ultrasonic transducer block, according to some embodiments.

FIGS. 25A and 25B illustrate another example phase delay pattern for a5×5 ultrasonic transducer block, according to some embodiments.

FIG. 26 illustrates example simultaneous operation of transmitter blocksfor a multiple array positions in a two-dimensional array of ultrasonictransducers, according to some embodiments.

FIG. 27 illustrates an example operational model of a transmit signal toa receive signal of a two-dimensional array of ultrasonic transducers,according to some embodiments.

FIG. 28 illustrates an example transmit path architecture of atwo-dimensional array of ultrasonic transducers, according to someembodiments.

FIG. 29 illustrates an example receive path architecture of atwo-dimensional array of ultrasonic transducers, according to someembodiments.

FIGS. 30A-30B illustrate a portion of a PMUT, such as shown in FIG. 26,wherein FIG. 30A depicts successful transmit (Tx) and receive (Rx)patterns and FIG. 30B depicts degradation of the patterns due totruncation at the edges of the grid, according to some embodiments.

FIG. 31 illustrates an area of an array, such as shown in FIG. 26, inwhich the area is covered by two or three successive scans, according tosome embodiments.

FIG. 32 is a flow chart is a flow chart illustrating one embodiment of amethod for generating an image.

FIGS. 33A-33B illustrate a portion of a PMUT, such as shown in FIG. 26,wherein FIG. 33A depicts another set of successful Tx and Rx patternsand FIG. 33B depicts yet another set of successful Tx and Rx patterns,to generate an image produced by three scans, according to someembodiments.

FIG. 34 illustrates an area of an array, such as shown in FIG. 26, inwhich the area is covered by three or five successive scans, accordingto some embodiments.

FIGS. 35A-35D illustrate a 2×5 PMUT, similar to that shown in FIG. 26,in which scans are made of edge pixel patterns, namely, top (FIG. 35A),bottom (FIG. 35B), left (FIG. 35C), and right (FIG. 35D), to generate animage produced by five scans, according to some embodiments.

DESCRIPTION OF EMBODIMENTS

The following Description of Embodiments is merely provided by way ofexample and not of limitation. Furthermore, there is no intention to bebound by any expressed or implied theory presented in the precedingbackground or in the following Description of Embodiments.

Reference will now be made in detail to various embodiments of thesubject matter, examples of which are illustrated in the accompanyingdrawings. While various embodiments are discussed herein, it will beunderstood that they are not intended to limit to these embodiments. Onthe contrary, the presented embodiments are intended to coveralternatives, modifications and equivalents, which may be includedwithin the spirit and scope the various embodiments as defined by theappended claims. Furthermore, in this Description of Embodiments,numerous specific details are set forth in order to provide a thoroughunderstanding of embodiments of the present subject matter. However,embodiments may be practiced without these specific details. In otherinstances, well known methods, procedures, components, and circuits havenot been described in detail as not to unnecessarily obscure aspects ofthe described embodiments.

Notation and Nomenclature

Some portions of the detailed descriptions which follow are presented interms of procedures, logic blocks, processing and other symbolicrepresentations of operations on data within an electrical device. Thesedescriptions and representations are the means used by those skilled inthe data processing arts to most effectively convey the substance oftheir work to others skilled in the art. In the present application, aprocedure, logic block, process, or the like, is conceived to be one ormore self-consistent procedures or instructions leading to a desiredresult. The procedures are those requiring physical manipulations ofphysical quantities. Usually, although not necessarily, these quantitiestake the form of acoustic (e.g., ultrasonic) signals capable of beingtransmitted and received by an electronic device and/or electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated in an electrical device.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the description ofembodiments, discussions utilizing terms such as “capturing,”“combining,” “adding,” “replacing,” “transmitting,” “receiving,”“sensing,” “generating,” “imaging,” or the like, refer to the actionsand processes of an electronic device such as an electrical device.

Embodiments described herein may be discussed in the general context ofprocessor-executable instructions residing on some form ofnon-transitory processor-readable medium, such as program modules,executed by one or more computers or other devices. Generally, programmodules include routines, programs, objects, components, datastructures, etc., that perform particular tasks or implement particularabstract data types. The functionality of the program modules may becombined or distributed as desired in various embodiments.

In the figures, a single block may be described as performing a functionor functions; however, in actual practice, the function or functionsperformed by that block may be performed in a single component or acrossmultiple components, and/or may be performed using hardware, usingsoftware, or using a combination of hardware and software. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, logic, circuits, and stepshave been described generally in terms of their functionality. Whethersuch functionality is implemented as hardware or software depends uponthe particular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure. Also, the example systems describedherein may include components other than those shown, includingwell-known components.

Various techniques described herein may be implemented in hardware,software, firmware, or any combination thereof, unless specificallydescribed as being implemented in a specific manner. Any featuresdescribed as modules or components may also be implemented together inan integrated logic device or separately as discrete but interoperablelogic devices. If implemented in software, the techniques may berealized at least in part by a non-transitory processor-readable storagemedium comprising instructions that, when executed, perform one or moreof the methods described herein. The non-transitory processor-readabledata storage medium may form part of a computer program product, whichmay include packaging materials.

The non-transitory processor-readable storage medium may comprise randomaccess memory (RAM) such as synchronous dynamic random access memory(SDRAM), read only memory (ROM), non-volatile random access memory(NVRAM), electrically erasable programmable read-only memory (EEPROM),FLASH memory, other known storage media, and the like. The techniquesadditionally, or alternatively, may be realized at least in part by aprocessor-readable communication medium that carries or communicatescode in the form of instructions or data structures and that can beaccessed, read, and/or executed by a computer or other processor.

Various embodiments described herein may be executed by one or moreprocessors, such as one or more motion processing units (MPUs), sensorprocessing units (SPUs), host processor(s) or core(s) thereof, digitalsignal processors (DSPs), general purpose microprocessors, applicationspecific integrated circuits (ASICs), application specific instructionset processors (ASIPs), field programmable gate arrays (FPGAs), aprogrammable logic controller (PLC), a complex programmable logic device(CPLD), a discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein, or other equivalent integrated or discrete logiccircuitry. The term “processor,” as used herein may refer to any of theforegoing structures or any other structure suitable for implementationof the techniques described herein. As is employed in the subjectspecification, the term “processor” can refer to substantially anycomputing processing unit or device comprising, but not limited tocomprising, single-core processors; single-processors with softwaremultithread execution capability; multi-core processors; multi-coreprocessors with software multithread execution capability; multi-coreprocessors with hardware multithread technology; parallel platforms; andparallel platforms with distributed shared memory. Moreover, processorscan exploit nano-scale architectures such as, but not limited to,molecular and quantum-dot based transistors, switches and gates, inorder to optimize space usage or enhance performance of user equipment.A processor may also be implemented as a combination of computingprocessing units.

In addition, in some aspects, the functionality described herein may beprovided within dedicated software modules or hardware modulesconfigured as described herein. Also, the techniques could be fullyimplemented in one or more circuits or logic elements. A general purposeprocessor may be a microprocessor, but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of an SPU/MPU and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with an SPU core, MPU core, or any othersuch configuration.

Overview of Discussion

Discussion begins with a description of an example PiezoelectricMicromachined Ultrasonic Transducer (PMUT), in accordance with variousembodiments. Example arrays including PMUT devices are then described.Example operations of the example arrays of PMUT devices are thenfurther described. Example sensor configurations for generating an imageare then described.

A conventional piezoelectric ultrasonic transducer able to generate anddetect pressure waves can include a membrane with the piezoelectricmaterial, a supporting layer, and electrodes combined with a cavitybeneath the electrodes. Miniaturized versions are referred to as PMUTs.Typical PMUTs use an edge anchored membrane or diaphragm that maximallyoscillates at or near the center of the membrane at a resonant frequency(f) proportional to h/a², where h is the thickness, and a is the radiusof the membrane. Higher frequency membrane oscillations can be createdby increasing the membrane thickness, decreasing the membrane radius, orboth. Increasing the membrane thickness has its limits, as the increasedthickness limits the displacement of the membrane. Reducing the PMUTmembrane radius also has limits, because a larger percentage of PMUTmembrane area is used for edge anchoring.

Embodiments described herein relate to a PMUT device for ultrasonic wavegeneration and sensing. In accordance with various embodiments, an arrayof such PMUT devices is described. The PMUT includes a substrate and anedge support structure connected to the substrate. A membrane isconnected to the edge support structure such that a cavity is definedbetween the membrane and the substrate, where the membrane is configuredto allow movement at ultrasonic frequencies. The membrane includes apiezoelectric layer and first and second electrodes coupled to opposingsides of the piezoelectric layer. An interior support structure isdisposed within the cavity and connected to the substrate and themembrane. In some embodiments, the interior support structure may beomitted.

The described PMUT device and array of PMUT devices can be used forgeneration of acoustic signals or measurement of acoustically senseddata in various applications, such as, but not limited to, medicalapplications, security systems, biometric systems (e.g., fingerprintsensors and/or motion/gesture recognition sensors), mobile communicationsystems, industrial automation systems, consumer electronic devices,robotics, etc. In one embodiment, the PMUT device can facilitateultrasonic signal generation and sensing (transducer). Moreover,embodiments described herein provide a sensing component including asilicon wafer having a two-dimensional (or one-dimensional) array ofultrasonic transducers.

Embodiments described herein provide a PMUT that operates at a highfrequency for reduced acoustic diffraction through high acousticvelocity materials (e.g., glass, metal), and for shorter pulses so thatspurious secondary or undesired reflections can be time-gated out.Embodiments described herein also provide a PMUT that has a low qualityfactor providing a shorter ring-up and ring-down time to allow betterrejection of spurious reflections by time-gating. Embodiments describedherein also provide a PMUT that has a high fill-factor providing forlarge transmit and receive signals.

Embodiments described herein provide for generation of an image using anultrasonic sensor based on capturing different sets of pixels capturedusing different beamforming patterns. For instance, a first set ofpixels is captured at an ultrasonic sensor using a first beamformingpattern, wherein the first beamforming pattern includes a first patternof ultrasonic transducers of the ultrasonic sensor. A second set ofpixels is captured at the ultrasonic sensor using a second beamformingpattern, wherein the second beamforming pattern includes a secondpattern of ultrasonic transducers, wherein the second beamformingpattern is different than the first beamforming pattern, and wherein thesecond set of pixels corresponds to an edge region of the ultrasonicsensor. The first set of pixels and the second set of pixels arecombined to form the image. In one embodiment, the first set of pixelsis added to the second set of pixels to form the image. In anotherembodiment, pixels of the first set of pixels corresponding to the edgeregion are replaced with the second set of pixels to form the image.

Piezoelectric Micromachined Ultrasonic Transducer (PMUT)

Systems and methods disclosed herein, in one or more aspects provideefficient structures for an acoustic transducer (e.g., a piezoelectricactuated transducer or PMUT). One or more embodiments are now describedwith reference to the drawings, wherein like reference numerals are usedto refer to like elements throughout. In the following description, forpurposes of explanation, numerous specific details are set forth inorder to provide a thorough understanding of the various embodiments. Itmay be evident, however, that the various embodiments can be practicedwithout these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order tofacilitate describing the embodiments in additional detail.

As used in this application, the term “or” is intended to mean aninclusive “or” rather than an exclusive “or”. That is, unless specifiedotherwise, or clear from context, “X employs A or B” is intended to meanany of the natural inclusive permutations. That is, if X employs A; Xemploys B; or X employs both A and B, then “X employs A or B” issatisfied under any of the foregoing instances. In addition, thearticles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. In addition, the word “coupled” is used herein to mean direct orindirect electrical or mechanical coupling. In addition, the word“example” is used herein to mean serving as an example, instance, orillustration.

FIG. 1A is a diagram illustrating a PMUT device 100 having a centerpinned membrane, according to some embodiments. PMUT device 100 includesan interior pinned membrane 120 positioned over a substrate 140 todefine a cavity 130. In one embodiment, membrane 120 is attached both toa surrounding edge support 102 and interior support 104. In oneembodiment, edge support 102 is connected to an electric potential. Edgesupport 102 and interior support 104 may be made of electricallyconducting materials, such as and without limitation, aluminum,molybdenum, or titanium. Edge support 102 and interior support 104 mayalso be made of dielectric materials, such as silicon dioxide, siliconnitride or aluminum oxide that have electrical connections on theirsides or in vias through edge support 102 or interior support 104,electrically coupling lower electrode 106 to electrical wiring insubstrate 140.

In one embodiment, both edge support 102 and interior support 104 areattached to a substrate 140. In various embodiments, substrate 140 mayinclude at least one of, and without limitation, silicon or siliconnitride. It should be appreciated that substrate 140 may includeelectrical wirings and connection, such as aluminum or copper. In oneembodiment, substrate 140 includes a CMOS logic wafer bonded to edgesupport 102 and interior support 104. In one embodiment, the membrane120 comprises multiple layers. In an example embodiment, the membrane120 includes lower electrode 106, piezoelectric layer 110, and upperelectrode 108, where lower electrode 106 and upper electrode 108 arecoupled to opposing sides of piezoelectric layer 110. As shown, lowerelectrode 106 is coupled to a lower surface of piezoelectric layer 110and upper electrode 108 is coupled to an upper surface of piezoelectriclayer 110. It should be appreciated that, in various embodiments, PMUTdevice 100 is a microelectromechanical (MEMS) device.

In one embodiment, membrane 120 also includes a mechanical support layer112 (e.g., stiffening layer) to mechanically stiffen the layers. Invarious embodiments, mechanical support layer 140 may include at leastone of, and without limitation, silicon, silicon oxide, silicon nitride,aluminum, molybdenum, titanium, etc. In one embodiment, PMUT device 100also includes an acoustic coupling layer 114 above membrane 120 forsupporting transmission of acoustic signals. It should be appreciatedthat acoustic coupling layer can include air, liquid, gel-likematerials, or other materials for supporting transmission of acousticsignals. In one embodiment, PMUT device 100 also includes platen layer116 above acoustic coupling layer 114 for containing acoustic couplinglayer 114 and providing a contact surface for a finger or other sensedobject with PMUT device 100. It should be appreciated that, in variousembodiments, acoustic coupling layer 114 provides a contact surface,such that platen layer 116 is optional. Moreover, it should beappreciated that acoustic coupling layer 114 and/or platen layer 116 maybe included with or used in conjunction with multiple PMUT devices. Forexample, an array of PMUT devices may be coupled with a single acousticcoupling layer 114 and/or platen layer 116.

FIG. 1B is identical to FIG. 1A in every way, except that the PMUTdevice 100′ of FIG. 1B omits the interior support 104 and thus membrane120 is not pinned (e.g., is “unpinned”). There may be instances in whichan unpinned membrane 120 is desired. However, in other instances, apinned membrane 120 may be employed.

FIG. 2 is a diagram illustrating an example of membrane movement duringactivation of pinned PMUT device 100, according to some embodiments. Asillustrated with respect to FIG. 2, in operation, responsive to anobject proximate platen layer 116, the electrodes 106 and 108 deliver ahigh frequency electric charge to the piezoelectric layer 110, causingthose portions of the membrane 120 not pinned to the surrounding edgesupport 102 or interior support 104 to be displaced upward into theacoustic coupling layer 114. This generates a pressure wave that can beused for signal probing of the object. Return echoes can be detected aspressure waves causing movement of the membrane, with compression of thepiezoelectric material in the membrane causing an electrical signalproportional to amplitude of the pressure wave.

The described PMUT device 100 can be used with almost any electricaldevice that converts a pressure wave into mechanical vibrations and/orelectrical signals. In one aspect, the PMUT device 100 can comprise anacoustic sensing element (e.g., a piezoelectric element) that generatesand senses ultrasonic sound waves. An object in a path of the generatedsound waves can create a disturbance (e.g., changes in frequency orphase, reflection signal, echoes, etc.) that can then be sensed. Theinterference can be analyzed to determine physical parameters such as(but not limited to) distance, density and/or speed of the object. As anexample, the PMUT device 100 can be utilized in various applications,such as, but not limited to, fingerprint or physiologic sensors suitablefor wireless devices, industrial systems, automotive systems, robotics,telecommunications, security, medical devices, etc. For example, thePMUT device 100 can be part of a sensor array comprising a plurality ofultrasonic transducers deposited on a wafer, along with various logic,control and communication electronics. A sensor array may comprisehomogenous or identical PMUT devices 100, or a number of different orheterogonous device structures.

In various embodiments, the PMUT device 100 employs a piezoelectriclayer 110, comprised of materials such as, but not limited to, aluminumnitride (AlN), lead zirconate titanate (PZT), quartz, polyvinylidenefluoride (PVDF), and/or zinc oxide, to facilitate both acoustic signalproduction and sensing. The piezoelectric layer 110 can generateelectric charges under mechanical stress and conversely experience amechanical strain in the presence of an electric field. For example, thepiezoelectric layer 110 can sense mechanical vibrations caused by anultrasonic signal and produce an electrical charge at the frequency(e.g., ultrasonic frequency) of the vibrations. Additionally, thepiezoelectric layer 110 can generate an ultrasonic wave by vibrating inan oscillatory fashion that might be at the same frequency (e.g.,ultrasonic frequency) as an input current generated by an alternatingcurrent (AC) voltage applied across the piezoelectric layer 110. Itshould be appreciated that the piezoelectric layer 110 can includealmost any material (or combination of materials) that exhibitspiezoelectric properties, such that the structure of the material doesnot have a center of symmetry and a tensile or compressive stressapplied to the material alters the separation between positive andnegative charge sites in a cell causing a polarization at the surface ofthe material. The polarization is directly proportional to the appliedstress and is direction dependent so that compressive and tensilestresses results in electric fields of opposite polarizations.

Further, the PMUT device 100 comprises electrodes 106 and 108 thatsupply and/or collect the electrical charge to/from the piezoelectriclayer 110. It should be appreciated that electrodes 106 and 108 can becontinuous and/or patterned electrodes (e.g., in a continuous layerand/or a patterned layer). For example, as illustrated, electrode 106 isa patterned electrode and electrode 108 is a continuous electrode. As anexample, electrodes 106 and 108 can be comprised of almost any metallayers, such as, but not limited to, aluminum (Al), titanium (Ti),molybdenum (Mo), etc., which are coupled with and on opposing sides ofthe piezoelectric layer 110. In one embodiment, PMUT device alsoincludes a third electrode, as illustrated in FIG. 10 and describedbelow.

According to an embodiment, the acoustic impedance of acoustic couplinglayer 114 is selected to be similar to the acoustic impedance of theplaten layer 116, such that the acoustic wave is efficiently propagatedto/from the membrane 120 through acoustic coupling layer 114 and platenlayer 116. As an example, the platen layer 116 can comprise variousmaterials having an acoustic impedance in the range between 0.8 to 4Mega Rayleigh (MRayl), such as, but not limited to, plastic, resin,rubber, Teflon, epoxy, etc. In another example, the platen layer 116 cancomprise various materials having a high acoustic impedance (e.g., anacoustic impendence greater than 10 MRayl), such as, but not limited to,glass, aluminum-based alloys, sapphire, etc. Typically, the platen layer116 can be selected based on an application of the sensor. For instance,in fingerprinting applications, platen layer 116 can have an acousticimpedance that matches (e.g., exactly or approximately) the acousticimpedance of human skin (e.g., 1.6×10⁶ Rayl). Further, in one aspect,the platen layer 116 can further include a thin layer of anti-scratchmaterial. In various embodiments, the anti-scratch layer of the platenlayer 116 is less than the wavelength of the acoustic wave that is to begenerated and/or sensed to provide minimum interference duringpropagation of the acoustic wave. As an example, the anti-scratch layercan comprise various hard and scratch-resistant materials (e.g., havinga Mohs hardness of over 7 on the Mohs scale), such as, but not limitedto sapphire, glass, titanium nitride (TiN), silicon carbide (SiC),diamond, etc. As an example, PMUT device 100 can operate at 20 MHz andaccordingly, the wavelength of the acoustic wave propagating through theacoustic coupling layer 114 and platen layer 116 can be 70-150 microns.In this example scenario, insertion loss can be reduced and acousticwave propagation efficiency can be improved by utilizing an anti-scratchlayer having a thickness of 1 micron and the platen layer 116 as a wholehaving a thickness of 1-2 millimeters. It is noted that the term“anti-scratch material” as used herein relates to a material that isresistant to scratches and/or scratch-proof and provides substantialprotection against scratch marks.

In accordance with various embodiments, the PMUT device 100 can includemetal layers (e.g., aluminum (Al), titanium (Ti), molybdenum (Mo), etc.)patterned to form electrode 106 in particular shapes (e.g., ring,circle, square, octagon, hexagon, etc.) that are defined in-plane withthe membrane 120. Electrodes can be placed at a maximum strain area ofthe membrane 120 or placed at close to either or both the surroundingedge support 102 and interior support 104. Furthermore, in one example,electrode 108 can be formed as a continuous layer providing a groundplane in contact with mechanical support layer 112, which can be formedfrom silicon or other suitable mechanical stiffening material. In stillother embodiments, the electrode 106 can be routed along the interiorsupport 104, advantageously reducing parasitic capacitance as comparedto routing along the edge support 102.

For example, when actuation voltage is applied to the electrodes, themembrane 120 will deform and move out of plane. The motion then pushesthe acoustic coupling layer 114 it is in contact with and an acoustic(ultrasonic) wave is generated. Oftentimes, vacuum is present inside thecavity 130 and therefore damping contributed from the media within thecavity 130 can be ignored. However, the acoustic coupling layer 114 onthe other side of the membrane 120 can substantially change the dampingof the PMUT device 100. For example, a quality factor greater than 20can be observed when the PMUT device 100 is operating in air withatmosphere pressure (e.g., acoustic coupling layer 114 is air) and candecrease lower than 2 if the PMUT device 100 is operating in water(e.g., acoustic coupling layer 114 is water).

FIG. 3 is a top view of the PMUT device 100 of FIG. 1A having asubstantially square shape, which corresponds in part to a cross sectionalong dotted line 101 in FIG. 3. Layout of surrounding edge support 102,interior support 104, and lower electrode 106 are illustrated, withother continuous layers not shown. It should be appreciated that theterm “substantially” in “substantially square shape” is intended toconvey that a PMUT device 100 is generally square-shaped, withallowances for variations due to manufacturing processes and tolerances,and that slight deviation from a square shape (e.g., rounded corners,slightly wavering lines, deviations from perfectly orthogonal corners orintersections, etc.) may be present in a manufactured device. While agenerally square arrangement PMUT device is shown, alternativeembodiments including rectangular, hexagon, octagonal, ring, circular,or elliptical are contemplated. In other embodiments, more complexelectrode or PMUT device shapes can be used, including irregular andnon-symmetric layouts such as chevrons or pentagons for edge support andelectrodes.

FIG. 4 is a simulated topographic map 400 illustrating maximum verticaldisplacement of the membrane 120 of the PMUT device 100 shown in FIGS.1A-3. As indicated, maximum displacement generally occurs along a centeraxis of the lower electrode, with corner regions having the greatestdisplacement. As with the other figures, FIG. 4 is not drawn to scalewith the vertical displacement exaggerated for illustrative purposes,and the maximum vertical displacement is a fraction of the horizontalsurface area comprising the PMUT device 100. In an example PMUT device100, maximum vertical displacement may be measured in nanometers, whilesurface area of an individual PMUT device 100 may be measured in squaremicrons.

FIG. 5 is a top view of another example of the PMUT device 100 of FIG.1A having a substantially circular or ring shape, which corresponds inpart to a cross section along dotted line 101 in FIG. 5. Layout ofsurrounding edge support 102, interior support 104, and lower electrode106 are illustrated, with other continuous layers not shown. It shouldbe appreciated that the term “substantially” in “substantially circularshape” is intended to convey that a PMUT device 100 is generallycircle-shaped, with allowances for variations due to manufacturingprocesses and tolerances, and that slight deviation from a circle shape(e.g., slight deviations on radial distance from center, etc.) may bepresent in a manufactured device.

FIG. 6 is a top view of another example of the PMUT device 100 of FIG.1A having a substantially hexagonal shape, which corresponds in part toa cross section along dotted line 101 in FIG. 6. Layout of surroundingedge support 102, interior support 104, and lower electrode 106 areillustrated, with other continuous layers not shown. It should beappreciated that the term “substantially” in “substantially hexagonalshape” is intended to convey that a PMUT device 100 is generallyhexagon-shaped, with allowances for variations due to manufacturingprocesses and tolerances, and that slight deviation from a hexagon shape(e.g., rounded corners, slightly wavering lines, deviations fromperfectly orthogonal corners or intersections, etc.) may be present in amanufactured device.

FIG. 7 illustrates an example two-dimensional array 700 ofcircular-shaped PMUT devices 701 formed from PMUT devices having asubstantially circular shape similar to that discussed in conjunctionwith FIGS. 1A, 2 and 5. Layout of circular surrounding edge support 702,interior support 704, and annular or ring shaped lower electrode 706surrounding the interior support 704 are illustrated, while othercontinuous layers are not shown for clarity. As illustrated, array 700includes columns of circular-shaped PMUT devices 701 that are offset.However, in some embodiments, the columns of circular-shaped PMUTdevices 701 are not offset. It should be appreciated that thecircular-shaped PMUT devices 701 may be closer together, such that edgesof the columns of circular-shaped PMUT devices 701 overlap. Moreover, itshould be appreciated that circular-shaped PMUT devices 701 may contacteach other. In various embodiments, adjacent circular-shaped PMUTdevices 701 are electrically isolated. In other embodiments, groups ofadjacent circular-shaped PMUT devices 701 are electrically connected,where the groups of adjacent circular-shaped PMUT devices 701 areelectrically isolated.

FIG. 8 illustrates an example two-dimensional array 800 of square-shapedPMUT devices 801 formed from PMUT devices having a substantially squareshape similar to that discussed in conjunction with FIGS. 1A, 2 and 3.Layout of square surrounding edge support 802, interior support 804, andsquare-shaped lower electrode 806 surrounding the interior support 804are illustrated, while other continuous layers are not shown forclarity. As illustrated, array 800 includes columns of square-shapedPMUT devices 801 that are in rows and columns. It should be appreciatedthat rows or columns of the square-shaped PMUT devices 801 may beoffset. Moreover, it should be appreciated that square-shaped PMUTdevices 801 may contact each other or be spaced apart. In variousembodiments, adjacent square-shaped PMUT devices 801 are electricallyisolated. In other embodiments, groups of adjacent square-shaped PMUTdevices 801 are electrically connected, where the groups of adjacentsquare-shaped PMUT devices 801 are electrically isolated.

FIG. 9 illustrates an example two-dimensional array 900 ofhexagon-shaped PMUT devices 901 formed from PMUT devices having asubstantially hexagon shape similar to that discussed in conjunctionwith FIGS. 1A, 2 and 6. Layout of hexagon-shaped surrounding edgesupport 902, interior support 904, and hexagon-shaped lower electrode906 surrounding the interior support 904 are illustrated, while othercontinuous layers are not shown for clarity. It should be appreciatedthat rows or columns of the hexagon-shaped PMUT devices 901 may beoffset. Moreover, it should be appreciated that hexagon-shaped PMUTdevices 901 may contact each other or be spaced apart. In variousembodiments, adjacent hexagon-shaped PMUT devices 901 are electricallyisolated. In other embodiments, groups of adjacent hexagon-shaped PMUTdevices 901 are electrically connected, where the groups of adjacenthexagon-shaped PMUT devices 901 are electrically isolated. While FIGS.7, 8 and 9 illustrate example layouts of PMUT devices having differentshapes, it should be appreciated that many different layouts areavailable. Moreover, in accordance with various embodiments, arrays ofPMUT devices are included within a MEMS layer.

In operation, during transmission, selected sets of PMUT devices in thetwo-dimensional array can transmit an acoustic signal (e.g., a shortultrasonic pulse) and during sensing, the set of active PMUT devices inthe two-dimensional array can detect an interference of the acousticsignal with an object (in the path of the acoustic wave). The receivedinterference signal (e.g., generated based on reflections, echoes, etc.of the acoustic signal from the object) can then be analyzed. As anexample, an image of the object, a distance of the object from thesensing component, a density of the object, a motion of the object,etc., can all be determined based on comparing a frequency and/or phaseof the interference signal with a frequency and/or phase of the acousticsignal. Moreover, results generated can be further analyzed or presentedto a user via a display device (not shown).

FIG. 10 illustrates a pair of example PMUT devices 1000 in a PMUT array,with each PMUT sharing at least one common edge support 1002. Asillustrated, the PMUT devices have two sets of independent lowerelectrode labeled as 1006 and 1026. These differing electrode patternsenable antiphase operation of the PMUT devices 1000, and increaseflexibility of device operation. In one embodiment, the pair of PMUTsmay be identical, but the two electrodes could drive different parts ofthe same PMUT antiphase (one contracting, and one extending), such thatthe PMUT displacement becomes larger. While other continuous layers arenot shown for clarity, each PMUT also includes an upper electrode (e.g.,upper electrode 108 of FIG. 1A). Accordingly, in various embodiments, aPMUT device may include at least three electrodes.

FIGS. 11A, 11B, 11C, and 11D illustrate alternative examples of interiorsupport structures, in accordance with various embodiments. Interiorsupports structures may also be referred to as “pinning structures,” asthey operate to pin the membrane to the substrate. It should beappreciated that interior support structures may be positioned anywherewithin a cavity of a PMUT device, and may have any type of shape (orvariety of shapes), and that there may be more than one interior supportstructure within a PMUT device. While FIGS. 11A, 11B, 11C, and 11Dillustrate alternative examples of interior support structures, itshould be appreciated that these examples or for illustrative purposes,and are not intended to limit the number, position, or type of interiorsupport structures of PMUT devices.

For example, interior supports structures do not have to be centrallylocated with a PMUT device area, but can be non-centrally positionedwithin the cavity. As illustrated in FIG. 11A, interior support 1104 ais positioned in a non-central, off-axis position with respect to edgesupport 1102. In other embodiments such as seen in FIG. 11B, multipleinterior supports 1104 b can be used. In this embodiment, one interiorsupport is centrally located with respect to edge support 1102, whilethe multiple, differently shaped and sized interior supports surroundthe centrally located support. In still other embodiments, such as seenwith respect to FIGS. 11C and 11D, the interior supports (respectively1104 c and 1104 d) can contact a common edge support 1102. In theembodiment illustrated in FIG. 11D, the interior supports 1104 d caneffectively divide the PMUT device into subpixels. This would allow, forexample, activation of smaller areas to generate high frequencyultrasonic waves, and sensing a returning ultrasonic echo with largerareas of the PMUT device. It will be appreciated that the individualpinning structures can be combined into arrays.

FIG. 12 illustrates an embodiment of a PMUT array used in an ultrasonicfingerprint sensing system 1250. The fingerprint sensing system 1250 caninclude a platen 1216 onto which a human finger 1252 may make contact.Ultrasonic signals are generated and received by a PMUT device array1200, and travel back and forth through acoustic coupling layer 1214 andplaten 1216. Signal analysis is conducted using processing logic module1240 (e.g., control logic) directly attached (via wafer bonding or othersuitable techniques) to the PMUT device array 1200. It will beappreciated that the size of platen 1216 and the other elementsillustrated in FIG. 12 may be much larger (e.g., the size of ahandprint) or much smaller (e.g., just a fingertip) than as shown in theillustration, depending on the particular application.

In this example for fingerprinting applications, the human finger 1252and the processing logic module 1240 can determine, based on adifference in interference of the acoustic signal with valleys and/orridges of the skin on the finger, an image depicting epi-dermis and/ordermis layers of the finger. Further, the processing logic module 1240can compare the image with a set of known fingerprint images tofacilitate identification and/or authentication. Moreover, in oneexample, if a match (or substantial match) is found, the identity ofuser can be verified. In another example, if a match (or substantialmatch) is found, a command/operation can be performed based on anauthorization rights assigned to the identified user. In yet anotherexample, the identified user can be granted access to a physicallocation and/or network/computer resources (e.g., documents, files,applications, etc.)

In another example, for finger-based applications, the movement of thefinger can be used for cursor tracking/movement applications. In suchembodiments, a pointer or cursor on a display screen can be moved inresponse to finger movement. It is noted that processing logic module1240 can include or be connected to one or more processors configured toconfer at least in part the functionality of system 1250. To that end,the one or more processors can execute code instructions stored inmemory, for example, volatile memory and/or nonvolatile memory.

FIG. 13 illustrates an integrated fingerprint sensor 1300 formed bywafer bonding a CMOS logic wafer and a MEMS wafer defining PMUT devices,according to some embodiments. FIG. 13 illustrates in partial crosssection one embodiment of an integrated fingerprint sensor formed bywafer bonding a substrate 1340 CMOS logic wafer and a MEMS waferdefining PMUT devices having a common edge support 1302 and separateinterior support 1304. For example, the MEMS wafer may be bonded to theCMOS logic wafer using aluminum and germanium eutectic alloys, asdescribed in U.S. Pat. No. 7,442,570. PMUT device 1300 has an interiorpinned membrane 1320 formed over a cavity 1330. The membrane 1320 isattached both to a surrounding edge support 1302 and interior support1304. The membrane 1320 is formed from multiple layers.

Example Operation of a Two-Dimensional Array of Ultrasonic Transducers

Systems and methods disclosed herein, in one or more aspects provide forthe operation of a two-dimensional array of ultrasonic transducers(e.g., an array of piezoelectric actuated transducers or PMUTs). One ormore embodiments are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the various embodiments. It may be evident, however,that the various embodiments can be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form in order to facilitate describing the embodimentsin additional detail.

FIG. 14 illustrates an example ultrasonic transducer system 1400 withphase delayed transmission, according to some embodiments. Asillustrated, FIG. 14 shows ultrasonic beam transmission and receptionusing a one-dimensional, five-element, ultrasonic transducer system 1400having phase delayed inputs 1410. In various embodiments, ultrasonictransducer system 1400 is comprised of PMUT devices having a centerpinned membrane (e.g., PMUT device 100 of FIG. 1A).

As illustrated, ultrasonic transducer system 1400 includes fiveultrasonic transducers 1402 including a piezoelectric material andactivating electrodes that are covered with a continuous stiffeninglayer 1404 (e.g., a mechanical support layer). Stiffening layer 1404contacts acoustic coupling layer 1406, and in turn is covered by aplaten layer 1408. In various embodiments, the stiffening layer 1404 canbe silicon, and the platen layer 1408 formed from glass, sapphire, orpolycarbonate or similar durable plastic. The intermediately positionedacoustic coupling layer 1406 can be formed from a plastic, epoxy, or gelsuch as polydimethylsiloxane (PDMS) or other material. In oneembodiment, the material of acoustic coupling layer 1406 has an acousticimpedance selected to be between the acoustic impedance of layers 1404and 1408. In one embodiment, the material of acoustic coupling layer1406 has an acoustic impedance selected to be close the acousticimpedance of platen layer 1408, to reduce unwanted acoustic reflectionsand improve ultrasonic beam transmission and sensing. However,alternative material stacks to the one shown in FIG. 14 may be used andcertain layers may be omitted, provided the medium through whichtransmission occurs passes signals in a predictable way.

In operation, and as illustrated in FIG. 14, the ultrasonic transducers1402 labelled with an “x” are triggered to emit ultrasonic waves at aninitial time. At a second time, (e.g., 1-100 nanoseconds later), theultrasonic transducers 1402 labelled with a “y” are triggered. At athird time (e.g., 1-100 nanoseconds after the second time) theultrasonic transducer 1402 labelled with a “z” is triggered. Theultrasonic waves transmitted at different times cause interference witheach other, effectively resulting in a single high intensity beam 1420that exits the platen layer 1408 at a focal point, contacts objects,such as a finger (not shown), that contact the platen layer 1408, and isin part reflected back to the ultrasonic transducers. In one embodiment,the ultrasonic transducers 1402 are switched from a transmission mode toa reception mode, allowing the “z” ultrasonic transducer to detect anyreflected signals 1422. In other words, the phase delay pattern of theultrasonic transducers 1402 is symmetric about the focal point wherehigh intensity beam 1420 exits platen layer 1408.

It should be appreciated that an ultrasonic transducer 1402 ofultrasonic transducer system 1400 may be used to transmit and/or receivean ultrasonic signal, and that the illustrated embodiment is anon-limiting example. The received signal (e.g., generated based onreflections, echoes, etc. of the acoustic signal from an objectcontacting or near the platen layer 1408) can then be analyzed. As anexample, an image of the object, a distance of the object from thesensing component, acoustic impedance of the object, a motion of theobject, etc., can all be determined based on comparing a frequency,amplitude, phase and/or arrival time of the received signal with afrequency, amplitude, phase and/or transmission time of the transmittedacoustic signal. Moreover, results generated can be further analyzed orpresented to a user via a display device (not shown).

FIG. 15 illustrates another example ultrasonic transducer system 1500with phase delayed transmission, according to some embodiments. Asillustrated, FIG. 15 shows ultrasonic beam transmission and receptionusing a virtual block of two-dimensional, 24-element, ultrasonictransducers that form a subset of a 40-element ultrasonic transducersystem 1500 having phase delayed inputs. In operation, an array position1530 (represented by the dotted line), also referred to herein as avirtual block, includes columns 1520, 1522 and 1524 of ultrasonictransducers 1502. At an initial time, columns 1520 and 1524 of arrayposition 1530 are triggered to emit ultrasonic waves at an initial time.At a second time (e.g., several nanoseconds later), column 1522 of arrayposition 1530 is triggered. The ultrasonic waves interfere with eachother, substantially resulting in emission of a high intensityultrasonic wave centered on column 1522. In one embodiment, theultrasonic transducers 1502 in columns 1520 and 1524 are switched off,while column 1522 is switched from a transmission mode to a receptionmode, allowing detection of any reflected signals.

In one embodiment, after the activation of ultrasonic transducers 1502of array position 1530, ultrasonic transducers 1502 of another arrayposition 1532, comprised of columns 1524, 1526, and 1528 of ultrasonictransducers 1502 are triggered in a manner similar to that described inthe foregoing description of array position 1530. In one embodiment,ultrasonic transducers 1502 of another array position 1532 are activatedafter a detection of a reflected ultrasonic signal at column 1522 ofarray position 1530. It should be appreciated that while movement of thearray position by two columns of ultrasonic transducers is illustrated,movement by one, three, or more columns rightward or leftward iscontemplated, as is movement by one or more rows, or by movement by bothsome determined number of rows and columns. In various embodiments,successive array positions can be either overlapping in part, or can bedistinct. In some embodiments, the size of array positions can bevaried. In various embodiments, the number of ultrasonic transducers1502 of an array position for emitting ultrasonic waves can be largerthan the number of ultrasonic transducers 1502 of an array position forultrasonic reception. In still other embodiments, array positions can besquare, rectangular, ellipsoidal, circular, or more complex shapes suchas crosses.

Example ultrasonic transducer system 1500 is operable to beamform a lineof a high intensity ultrasonic waves centered over column 1522. Itshould be appreciated that the principles illustrated in FIG. 15 forbeamforming a line using columns of ultrasonic transducers is applicableto embodiments for beamforming a point using ultrasonic transducersdriven by two-dimensional phase-delayed transmit signals, as will beexplained below. For instance, example ultrasonic transducer system 1500includes columns of ultrasonic transducers in which the ultrasonictransducers of each column are jointly operated to activate at the sametime, operating to beamform along a line. It should be appreciated thatthe ultrasonic transducers of a two-dimensional array may beindependently operable, and used for beamform points as well, as will bedescribed below.

FIG. 16 illustrates an example phase delay pattern for ultrasonic signaltransmission of a 9×9 ultrasonic transducer block 1600 of atwo-dimensional array of ultrasonic transducers, according to someembodiments. As illustrated in FIG. 16, each number in the ultrasonictransducer array is equivalent to the nanosecond delay used duringoperation, and an empty element (e.g., no number) in the ultrasonictransducer block 1600 means that an ultrasonic transducer is notactivated for signal transmission during operation. In variousembodiments, ultrasonic wave amplitude can be the same or similar foreach activated ultrasonic transducer, or can be selectively increased ordecreased relative to other ultrasonic transducers. In the illustratedpattern, initial ultrasonic transducer activation is limited to cornersof ultrasonic transducer block 1600, followed 10 nanoseconds later by arough ring around the edges of ultrasonic transducer block 1600. After23 nanoseconds, an interior ring of ultrasonic transducers is activated.Together, the twenty-four activated ultrasonic transducers generate anultrasonic beam centered on the ultrasonic transducer block 1600. Inother words, the phase delay pattern of ultrasonic transducer block 1600is symmetric about the focal point above the center of the 9×9transducer block where a high intensity beam contacts an object.

It should be appreciated that different ultrasonic transducers ofultrasonic transducer block 1600 may be activated for receipt ofreflected ultrasonic signals. For example, the center 3×3 ultrasonictransducers of ultrasonic transducer block 1600 may be activated toreceive the reflected ultrasonic signals. In another example, theultrasonic transducers used to transmit the ultrasonic signal are alsoused to receive the reflected ultrasonic signal. In another example, theultrasonic transducers used to receive the reflected ultrasonic signalsinclude at least one of the ultrasonic transducers also used to transmitthe ultrasonic signals.

FIG. 17 illustrates another example phase delay pattern for a 9×9ultrasonic transducer block 1700, according to some embodiments. Asillustrated in FIG. 17, the example phase delay pattern utilizesequidistant spacing of transmitting ultrasonic transducers. Asillustrated in FIG. 16, each number in the ultrasonic transducer arrayis equivalent to the nanosecond delay used during operation, and anempty element (e.g., no number) in the ultrasonic transducer block 1700means that an ultrasonic transducer is not activated for signaltransmission during operation. In the illustrated embodiment, theinitial ultrasonic transducer activation is limited to corners ofultrasonic transducer block 1700, followed 11 nanoseconds later by arough ring around the edges of ultrasonic transducer block 1700. After22 nanoseconds, an interior ring of ultrasonic transducers is activated.The illustrated embodiment utilizes equidistant spacing of thetransmitting ultrasonic transducers to reduce issues with crosstalk andheating, wherein each activated ultrasonic transducers is surrounded byun-activated ultrasonic transducers. Together, the twenty-four activatedultrasonic transducers generate an ultrasonic beam centered over theultrasonic transducer block 1700.

FIG. 18 illustrates a plan view 1800 of simulated ultrasonic pressure onthe focal plane for an example ultrasonic transducer system using threetiming phases, according to an embodiment. FIG. 18 is a graphicalillustration of simulated ultrasonic intensity for a three-phase systemsuch as discussed with respect to FIG. 17. In this embodiment, thecontour lines illustrate creation of a high intensity centrally locatedbeam capable of directing an approximately ˜50 to 100 um spot at aplaten layer. The illustrated beam linearly adds the energy from all 24actuated ultrasonic transducers and has a 3 dB beam width of 73 um.

FIG. 19 illustrates a cross section 1900 of simulated ultrasonicpressure on the focal plane for an example ultrasonic transducer systemusing either three or five timing phases, according to an embodiment.FIG. 19 is a graphical illustration of a cross section 1900 at line 1810of FIG. 18 of the simulated ultrasonic intensity for a three-phasesystem such as discussed with respect to FIG. 17. Also shown in FIG. 19is an example of the concentrated beam formed using five timing phasesand twenty-five actuated ultrasonic transducer, which illustratesnominally better performance but at increased complexity.

FIGS. 20A-C illustrate example transmitter blocks and receiver blocksfor an array position in a two-dimensional array 2000 of ultrasonictransducers, according to some embodiments. In FIG. 20A, a four phase(indicated using different hatch patterns) activated phase delay patternof ultrasonic transducers in a 9×9 array position 2010 is used togenerate an ultrasonic beam. Example receiver patterns are alsoillustrated, with receive pattern 2020 being ultrasonic transducers in a5×5 square and receive pattern 2022 being a more complex cross shapedblock.

In FIG. 20B, the 9×9 array position 2012 is moved rightward by a singlecolumn 2032 relative to array position 2010 of FIG. 20A, as indicated bythe arrow. In other words, after activation at array position 2010 oftwo-dimensional array 2000, array position 2012 of two-dimensional array2000 is activated, effectively sensing a pixel to the right oftwo-dimensional array 2000. In such a manner, multiple pixels associatedwith multiple array positions of the two-dimensional array 2000 can besensed. Similarly, in FIG. 20C the 9×9 array position 2014 is moveddownward by a single row 2034 relative to array position 2010 of FIG.20A after activation of array position 2010 of two-dimensional array2000, as indicated by the arrow. It should be appreciated that the 9×9array position can move to different positions of two-dimensional array2000 in any sequence. For example, an activation sequence may be definedas left to right for a row of ultrasonic transducers, then moving downone row when the end of a row is reached, and continuing to proceed inthis manner until a desired number of pixels are sensed. In anotherexample, the activation sequence may be defined as top to bottom for acolumn, and moving to another column once enough pixels have been sensedfor a column. It should be appreciated that any activation sequence maybe defined without limitation, including a random activation sequence.Moreover, it should be appreciated that any number of columns and/orrows can be skipped depending on a desired resolution.

In various embodiments, as an array position approaches an edge oftwo-dimensional array 2000, only those ultrasonic transducers that areavailable in two-dimensional array 2000 are activated. In other words,where a beam is being formed at a center of an array position, but thecenter is near or adjacent an edge of two-dimensional array 2000 suchthat at least one ultrasonic transducer of a phase delay pattern is notavailable (as the array position extends over an edge), then only thoseultrasonic transducers that are available in two-dimensional array 2000are activated. In various embodiments, the ultrasonic transducers thatare not available (e.g., outside the edge of two-dimensional array 2000)are truncated from the activation pattern. For example, for a 9×9ultrasonic transducer block, as the center ultrasonic transducer movestowards the edge such that the 9×9 ultrasonic transducer block extendsover the edge of the two-dimensional array, rows, columns, or rows andcolumns (in the instance of corners) of ultrasonic transducers aretruncated from the 9×9 ultrasonic transducer block. For instance, a 9×9ultrasonic transducer block effectively becomes a 5×9 ultrasonictransducer block when the center ultrasonic transducer is along an edgeof the two-dimensional array. Similarly, a 9×9 ultrasonic transducerblock effectively becomes a 6×9 ultrasonic transducer block when thecenter ultrasonic transducer is one row or column from an edge of thetwo-dimensional array. In other embodiments, as an array positionapproaches an edge of two-dimensional array 2000, the beam is steered byusing phase delay patterns that are asymmetric about the focal point, asdescribed below in accordance with FIGS. 21 through 25B.

FIG. 21 illustrates an example ultrasonic transducer system 2100 withphase delayed transmission, according to some embodiments. FIG. 21 showsfive different modes of ultrasonic beam transmission using an exampleone-dimensional, fifteen-element, ultrasonic transducer system 2100having phase delayed inputs. As illustrated, ultrasonic transducers 2102can be operated in various modes to provide ultrasonic beam spotsfocused along line 2150 (e.g., a top of a platen layer). In a firstmode, a single ultrasonic transducer 2152 is operated to provide asingle broad ultrasonic beam having a peak amplitude centered on arrow2153. In a second mode, multiple ultrasonic transducers in a symmetricalpattern 2154 about the center ultrasonic transducer are sequentiallytriggered to emit ultrasonic waves at differing initial times. Asillustrated, a center located transducer is triggered at a delayed timewith respect to surrounding transducers (which are triggeredsimultaneously). The ultrasonic waves interfere with each other,resulting in a single high intensity beam 2155. In a third mode, forultrasonic transducers 2156 located adjacent to or near an edge of theultrasonic transducer system 2100, an asymmetrical triggering patterncan be used to produce beam 2157. In a fourth mode, asymmetricaltriggering patterns for transducers 2158 can be used to steer anultrasound beam to an off-center location 2159. A shown, the focusedbeam 2159 can be directed to a point above and outside boundaries of theultrasonic transducer system 2100. In a fifth mode, the beam can besteered to focus at a series of discrete positions, with the beamspacing having a pitch less than, equal to, or greater than a pitch ofthe ultrasonic transducers. In FIG. 21, transducers 2160 are triggeredat separate times to produce beam spots separated by a pitch less thanthat of the ultrasonic transducers (indicated respectively by solidlines directed to form beam spot 2161 and dotted lines to form beam spot2163).

FIG. 22 illustrates an example ultrasonic transducer system 2200 withphase delayed transmission, according to some embodiments. Asillustrated, FIG. 22 shows ultrasonic beam transmission and receptionusing a one-dimensional, three-element, ultrasonic transducer system2200 having phase delayed inputs 2210. In various embodiments,ultrasonic transducer system 2200 is comprised of PMUT devices having acenter pinned membrane (e.g., PMUT device 100 of FIG. 1A).

As illustrated, ultrasonic transducer system 2200 includes threeultrasonic transducers 2202 including a piezoelectric material andactivating electrodes that are covered with a continuous stiffeninglayer 2204 (e.g., a mechanical support layer). Stiffening layer 2204contacts acoustic coupling layer 2206, and in turn is covered by aplaten layer 2208. In various embodiments, the stiffening layer 2204 canbe silicon, and the platen layer 2208 formed from glass, sapphire, orpolycarbonate or similar durable plastic. The intermediately positionedacoustic coupling layer 2206 can be formed from a plastic or gel such asPDMS or other material. In one embodiment, the material of acousticcoupling layer 2206 has an acoustic impedance selected to be between theacoustic impedance of layers 2204 and 2208. In one embodiment, thematerial of acoustic coupling layer 2206 has an acoustic impedanceselected to be close the acoustic impedance of platen layer 2208, toreduce unwanted acoustic reflections and improve ultrasonic beamtransmission and sensing. However, alternative material stacks to theone shown in FIG. 22 may be used and certain layers may be omitted,provided the medium through which transmission occurs passes signals ina predictable way.

In operation, and as illustrated in FIG. 22, the ultrasonic transducer2202 labelled with an “x” is triggered to emit ultrasonic waves at aninitial time. At a second time, (e.g., 1-100 nanoseconds later), theultrasonic transducer 2202 labelled with a “y” is triggered. At a thirdtime (e.g., 1-100 nanoseconds after the second time) the ultrasonictransducer 2202 labelled with a “z” is triggered. The ultrasonic wavestransmitted at different times cause interference with each other,effectively resulting in a single high intensity beam 2220 that exitsthe platen layer 2208, contacts objects, such as a finger (not shown),that contact the platen layer 2208, and is in part reflected back to theultrasonic transducers 2202. In one embodiment, the ultrasonictransducers 2202 are switched from a transmission mode to a receptionmode, allowing the “z” ultrasonic transducer to detect any reflectedsignals. In other words, the phase delay pattern of the ultrasonictransducers 2202 is asymmetric about the focal point where highintensity beam 2220 exits platen layer 2208.

It should be appreciated that an ultrasonic transducer 2202 ofultrasonic transducer system 2200 may be used to transmit and/or receivean ultrasonic signal, and that the illustrated embodiment is anon-limiting example. The received signal (e.g., generated based onreflections, echoes, etc. of the acoustic signal from an objectcontacting or near the platen layer 2208) can then be analyzed. As anexample, an image of the object, a distance of the object from thesensing component, an acoustic impedance of the object, a motion of theobject, etc., can all be determined based on comparing a frequency,amplitude and/or phase of the received interference signal with afrequency, amplitude and/or phase of the transmitted acoustic signal.Moreover, results generated can be further analyzed or presented to auser via a display device (not shown).

FIG. 23 illustrates another example ultrasonic transducer system 2300with phase delayed transmission, according to some embodiments. Asillustrated, FIG. 23 shows ultrasonic beam transmission and receptionusing a virtual block of two-dimensional, 16-element, ultrasonictransducers that form a subset of a 32-element ultrasonic transducersystem 2300 having phase delayed inputs. In operation, an array position2330 (represented by the dotted line), also referred to herein as avirtual block, includes columns 2322 and 2324 of ultrasonic transducers2302. At an initial time, column 2324 of array position 2330 istriggered to emit ultrasonic waves at an initial time. At a second time(e.g., several nanoseconds later), column 2322 of array position 2330 istriggered. The ultrasonic waves interfere with each other, substantiallyresulting in emission of a high intensity ultrasonic plane wave centeredon column 2322. In one embodiment, the ultrasonic transducers 2302 incolumn 2324 is switched off, while column 2322 is switched from atransmission mode to a reception mode, allowing detection of anyreflected signals.

In one embodiment, after the activation of ultrasonic transducers 2302of array position 2330, ultrasonic transducers 2302 of another arrayposition 2332, comprised of columns 2324, 2326, and 2328 of ultrasonictransducers 2302 are activated. In operation, at an initial time,columns 2324 and 2328 of array position 2332 are triggered to emitultrasonic waves at an initial time. At a second time (e.g., severalnanoseconds later), column 2326 of array position 2332 is triggered. Theultrasonic waves interfere with each other, substantially resulting inemission of a high intensity ultrasonic plane wave centered on column2326. In one embodiment, the ultrasonic transducers 2302 in columns 2324and 2328 are switched off, while column 2326 is switched from atransmission mode to a reception mode, allowing detection of anyreflected signals. In one embodiment, ultrasonic transducers 2302 ofanother array position 2332 are activated after a detection of areflected ultrasonic signal at column 2322 of array position 2330. Itshould be appreciated that while movement of the array position by twocolumns of ultrasonic transducers is illustrated, movement by one,three, or more columns rightward or leftward is contemplated, as ismovement by one or more rows, or by movement by both some determinednumber of rows and columns. In various embodiments, successive arraypositions can be either overlapping in part, or can be distinct. In someembodiments, the size of array positions can be varied. In variousembodiments, the number of ultrasonic transducers 2302 of an arrayposition for emitting ultrasonic waves can be larger than the number ofultrasonic transducers 2302 of an array position for ultrasonicreception. In still other embodiments, array positions can be square,rectangular, ellipsoidal, circular, or more complex shapes such ascrosses.

Example ultrasonic transducer system 2300 is operable to beamform a lineof a high intensity ultrasonic wave centered over a column of ultrasonictransducers. It should be appreciated that the principles illustrated inFIG. 23 for beamforming a line using columns of ultrasonic transducersis applicable to embodiments for beamforming a point using ultrasonictransducers, as will be explained below. For instance, exampleultrasonic transducer system 2300 includes columns of ultrasonictransducers in which the ultrasonic transducers of each column arejointly operated to activate at the same time, operating to beamformalong a line. It should be appreciated that the ultrasonic transducersof a two-dimensional array may be independently operable, and used forbeamform points as well, as will be described below.

FIGS. 24A, 24B, 25A and 25B illustrate example phase delay patterns fora 5×5 ultrasonic transducer blocks, according to some embodiments. Asillustrated in 24A, 24B, 25A and 25B, each number in the ultrasonictransducer array is equivalent to the nanosecond delay used duringoperation, and an empty element (e.g., no number) in the ultrasonictransducer blocks 2400, 2410, 2500 and 2510 means that an ultrasonictransducer is not activated for signal transmission during operation. Invarious embodiments, ultrasonic wave amplitude can be the same orsimilar for each activated ultrasonic transducer, or can be selectivelyincreased or decreased relative to other ultrasonic transducers. Itshould be appreciated that the phase delay patterns described inaccordance with FIGS. 24A, 24B, 25A and 25B are asymmetric about thefocal point where the resulting Tx beam contacts an object.

FIG. 24A illustrates an example phase delay pattern for an arrayposition of ultrasonic transducers at an edge of a two-dimensional arrayof ultrasonic transducers. Because ultrasonic transducer block 2400 islocated at an edge, a symmetrical phase delay pattern about a center ofultrasonic transducer block 2400 is not available. In the illustratedpattern, initial ultrasonic transducer activation is limited torightmost corners of the array, followed by selected action ofultrasonic transducers at 1, 4, 5, 6, and 8 nanosecond intervals.Together, the activated ultrasonic transducers generate an ultrasonicbeam centered on the 8 nanosecond delayed ultrasonic transducerindicated in gray. In one embodiment, so as to reduce issues withcrosstalk and heating, each activated ultrasonic transducer isequidistant from each other, being surrounded by un-activated ultrasonictransducer.

FIG. 24B illustrates an example phase delay pattern for a 5×5 ultrasonictransducer block 2410 in a corner of a two-dimensional array ofultrasonic transducers, with equidistant spacing of transmittingultrasonic transducers. Like the phase delay timing pattern of FIG. 24A,the initial ultrasonic transducer activation is asymmetrical. Together,the activated ultrasonic transducers generate an ultrasonic beamcentered on the 8 nanosecond delayed ultrasonic transducer indicated ingray. Adjacent ultrasonic transducers are activated in this embodimentto increase beam intensity.

FIG. 25A illustrates an example phase delay pattern for an arrayposition of ultrasonic transducers at an edge of a two-dimensional arrayof ultrasonic transducers. Because ultrasonic transducer block 2500 islocated at an edge, a symmetrical phase delay pattern about a center ofultrasonic transducer block 2500 is not available. In the illustratedpattern, initial ultrasonic transducer activation is limited torightmost corners of the array, followed by selected action ofultrasonic transducers at 1, 4, 5, 6, and 8 nanosecond intervals.Together, the activated ultrasonic transducers generate an ultrasonicbeam centered on the 8 nanosecond delayed ultrasonic transducerindicated in gray. After beam transmit concludes, the gray (8nanosecond) ultrasonic transducer is switched into a receive mode, alongwith those surrounding ultrasonic transducers indicated by spotted gray.

FIG. 25B illustrates ultrasonic transducer block 2510 is located at anedge of a two-dimensional array of ultrasonic transducers. This patternis formed as ultrasonic transducer block 2500 is moved up a single rowof ultrasonic transducers (indicated by arrow 2502) with respect to thephase delay pattern illustrated in FIG. 25A. As in FIG. 25A, theactivated ultrasonic transducers together generate an ultrasonic beamcentered on the 8 nanosecond delayed ultrasonic transducer indicated ingray. After beam transmit concludes, the gray (8 nanosecond) ultrasonictransducer is switched into a receive mode, along with those surroundingultrasonic transducers indicated by spotted gray.

FIG. 26 illustrates example simultaneous operation of transmitter blocksfor a multiple array positions in a two-dimensional array 2600 ofultrasonic transducers, according to some embodiments. As describedabove, a 9×9 array position can be used as a beamforming array for anultrasound transducer. In the illustrated example, two-dimensional array2600 is 144×48 ultrasonic transducers, separated into twelve identical24×24 blocks. In one embodiment, a mux-based transmission/receive(Tx/Rx) timing control method can be used to activate the appropriateultrasonic transducers in each block. When a sequence of activation togenerate an ultrasound beam and sensing reflected echoes is completed,the 9×9 array position is moved rightward or leftward, or upward anddownward, with respect to the drawing, and the sequence is repeateduntil substantially all ultrasonic transducers have emitted anultrasonic beam.

The PMUT sensor array can be comprised of 144×48 PMUT transducersarranged into a rectangular grid 2600 as shown in FIG. 26. However, thisis but one example of how the PMUT transducers may be arranged. Becausethe PMUT dimensions in this example are set at 70 μm×70 μm, theresulting sensor array area is 10.80 mm×3.36 mm. To allow for consistentreferencing of locations within the array, the long dimension is definedherein as the X-axis, the short dimension as the Y-axis, and bottom leftcorner as the origin. As such (using units of PMUTs as the coordinatesystem), the PMUT at the bottom left corner is at position (0, 0)whereas the one at the top right corner is at position (143, 47).

The two-dimensional array depicted in FIG. 26 comprises a 6×2 array ofsub-blocks 2602, each block comprising an array of 24×24 ultrasonictransducers, thereby providing a total of 144×48 ultrasonic transducersin the rectangular grid 2600. In another example, a 5×2 array ofsub-blocks can be used, each block comprising an array of 27×23ultrasonic transducers, thereby providing a total of 135×46 ultrasonictransducers in the rectangular grid. The resulting sensor array areawould be 9.45 mm×3.22 mm.

In order to capture fingerprint images as quickly as possible, it isdesired to simultaneously image as many pixels as possible. This islimited in practice by power consumption, number of independent receiver(Rx) channels (slices) and analog-to-digital converters (ADCs), andspacing requirements between active PMUTs required to avoidinterference. Accordingly, the capability to simultaneously captureseveral image pixels, e.g., 12 image pixels, may be implemented. It willbe appreciated that fewer than 12 or more than 12image pixels may becaptured simultaneously. In an embodiment, this involves 12 independent,parallel receiver channels and ADCs. Each of these receiver channels andADCs is associated with a subset of the overall sensor array as shown inFIG. 26. In this example, the 12 “PMUT Blocks” 2602 (also referred to as“ADC areas” or “array sub-blocks”) are 24×24 PMUTs in size. Thus, theultrasonic sensor may comprise a number, here, 12, of blocks ofultrasonic transducers.

The 12 Rx channels and ADCs are placed directly above or below eachassociated array sub-block. During a typical imaging operation, eacharray sub-block 2602 is configured and operated identically such that 12image pixels are captured simultaneously, one each from identicallocations within each array sub-block. A pattern of transmit (Tx) phasesis applied to selected PMUTs within each of the array sub-blocks 2602.The Tx phases are arranged to focus ultrasonic energy onto the area justabove the center of each of the patterns—a process called transmitbeamforming. The ultrasonic signal that is reflected back to the PMUTsat the center of each pattern is converted to an electrical signal androuted to the associated Rx channel and ADC for sensing and storage. Theoverall process of transmitting an ultrasonic signal, waiting for it topropagate to the target and back, and capturing the reflected ultrasonicsignal is referred to herein as a “TxRx Period”.

Imaging over the entire sensor area is accomplished by stepping the Txbeamforming patterns over the entire PMUT array, transmitting andreceiving at each location corresponding to an image pixel. Because 12image pixels are captured simultaneously during each TxRx Period (oneimage pixel from identical locations within each array sub-block 2602),it takes just as much time to capture the image pixels for the entirearray as it would to capture the image pixels for only a single arraysub-block.

There may be times when scanning is required over only a sub-set of thearray sub-blocks. In such cases, it is possible to disable transmittingor receiving signals within designated array sub-blocks to save thepower that would otherwise be used in transmitting or receiving withinthose sub-blocks. In one embodiment, the array is configured (e.g., viaa register) to enable transmitting in all 12 array sub-blocks. In otherembodiments, the array is configured to disable transmit within selectedvertical pairs of array sub-blocks. For example, setting bits of atransmit register to 1_0111 keeps array sub-blocks 0-5, 8, and 9 activefor transmit but shuts off transmit in array sub-blocks 6 and 7.Similarly, the array is configured (e.g., via a register) to enablereceiving in all 12 array sub-blocks. However, selected bits of thisregister can be set to “0” to disable receive within selected arraysub-blocks. For example, setting bits of a receive register to01_1011_1111 enables all the array sub-blocks to receive normally exceptfor array sub-blocks 6 and 9 (all receiver and ADC circuitry associatedwith array blocks 6 and 9 are powered down).

As previously described, it should be appreciated that any type ofactivation sequence may be used (e.g., side-to-side, top-to-bottom,random, another predetermined order, row and/or column skipping, etc.)Moreover, it should be appreciated that FIG. 26 illustrates a phasedelay pattern that is symmetric about a focal point of the transmittingpixels. As previously described, it is understood that different phasedelay patterns may be used as a focal point approaches or is adjacent toan edge and/or corner of the two-dimensional array. For example, a phasedelay pattern similar to that illustrated in FIG. 24A may be used as afocal point approaches or is adjacent to an edge of the two-dimensionalarray and a phase delay pattern similar to that illustrated in FIG. 24Bmay be used as a focal point approaches or is adjacent to corner of thetwo-dimensional array. In various embodiments, the ultrasonictransducers that are not available (e.g., outside the edge of atwo-dimensional array 2600) are truncated from the activation pattern.For example, for a 9×9 array position, as the center ultrasonictransducer moves towards an edge such that the 9×9 array positionextends over the edge of the two-dimensional array, rows, columns, orrows and columns (in the instance of corners) of ultrasonic transducersare truncated from the 9×9 array position. For instance, a 9×9 arrayposition effectively becomes a 5×9 array position when the centerultrasonic transducer is along an edge of the two-dimensional array.Similarly, a 9×9 ultrasonic transducer block effectively becomes a 6×9array position when the center ultrasonic transducer is one row orcolumn from an edge of the two-dimensional array.

FIG. 27 illustrates an example operational model 2700 of a transmitsignal to a receive signal of a two-dimensional array of ultrasonictransducers, according to some embodiments. FIG. 27 shows an operationalmodel 2700 from voltage transmit signal into a PMUT array 2710 andending with voltage receive signal from the PMUT array 2760. Threecycles of the voltage waveform are effectively bandpass filtered by thePMUT 2720, sent out as an ultrasonic pressure signal 2730 that isattenuated and delayed by interaction with an object 2740, and thenbandpass filtered by the PMUT array 2750 to create the final receivesignal 2760. In the illustrated example, the PMUT bandpass filterresponse 2720 and 2750 is assumed to be centered at 50 MHz with Q ofapproximately 3, although other values may be used.

FIG. 28 illustrates an example transmit path architecture 2800 of atwo-dimensional array of ultrasonic transducers, according to someembodiments. Achieving two-dimensional beamforming with high imageresolution under glass uses relatively high ultrasonic frequencies andprecise timing. Electronics to support a PMUT array with a centerfrequency of 50 MHz and a beamforming timing resolution of 1 nanosecondcan be used. The 50 MHz frequency can be generated by an on-chip RCoscillator and PLL that can be trimmed for sufficient accuracy by anoff-chip clock source. The beamforming resolution can be set by anon-chip PLL that outputs several timing phases that correspond to ˜3cycles of 50 MHz frequency and are appropriately delayed with respect toeach other. These phases can be routed to each PMUT according to thesel_(ph_map) signals shown in the FIG. 28.

FIG. 29 illustrates an example receive path architecture of atwo-dimensional array of ultrasonic transducers, according to someembodiments. The select lines 2910 correspond to rxColsel[k] forreceive, and the select lines 2920 correspond to rxRowsel[k] forreceive. Multiple PMUTs can be selected together for receiving thesignal. The signal from the PMUTs is fed into a front end receiver. Thesignal is then filtered to reduce noise outside of the signal bandwidth.The filtered signal is then integrated and digitized with an ADC. Insome embodiments, the PMUT and receiver layout allow straightforwardextension of the PMUT array size, since different applications canrequire different sensor array areas. The number of receiver slices willbe determined by the desired PMUT array size and minimum ultrasonictransducer separation between transmit beams. For example, in oneembodiment, a 20 ultrasonic transducer minimum separation betweenadjacent sets of active ultrasonic transducers reduces crosstalk.

Sensor Array Configurations

In some embodiments, a two-dimensional array of individual PMUT devices(e.g., PMUT device 100 of FIG. 1A or 100′ of FIG. 1B) corresponds with atwo-dimensional array of control electronics. This embodiment alsoapplies to other types of MEMS arrays with integrated controlelectronics. This includes, but is not limited to, applications forinertial sensors, optical devices, display devices, pressure sensors,microphones, inkjet printers, and other applications of MEMS technologywith integrated mixed-signal electronics for control. It should beappreciated that while the described embodiments may refer CMOS controlelements for controlling MEMS devices and/or PMUT devices, that thedescribed embodiments are not intended to be limited to suchimplementations.

FIGS. 30A-30B illustrate the effects on inner pixels when scanning withan XY-symmetrical pattern. Four sub-blocks 3002 are depicted. FIG. 30Ais an illustration of successful Tx/Rx patterns 3004 at a first patternstart, while FIG. 31 is an illustration of degradation of Tx/Rx patterns3006 due to truncation at the edges of a sub-block at a first patternend.

In accordance with the teachings herein, the degradation at the edges ofa sub-block 3002 may be alleviated by the following method in which afirst set of pixels is captured using a first beamforming pattern,wherein the first beamforming pattern comprises a first pattern ofultrasonic transducers of the ultrasonic sensor. Next, a second set ofpixels is captured using a second beamforming pattern, wherein thesecond beamforming pattern comprises a second pattern of ultrasonictransducers. The second beamforming pattern is different than the firstbeamforming pattern, and the second set of pixels corresponds to an edgeregion of the ultrasonic sensor. Finally, the first set of pixels andthe second set of pixels are combined to form the image.

FIG. 31 depicts the results of an area of the array covered by aninitial inner pixel pattern. A first set of pixels 3102 is scanned usingan inner pixel pattern that is XY symmetrical. Areas 3104 and 3106represent un-scanned pixels, which, if scanned using an XY symmetricalTx pattern, would suffer from truncated beamforming. Array areas 3104and 3106 represent areas that may suffer degradation from truncatedbeamforming.

There are two procedures that can be performed with captured pixels. Inthe first procedure, pixels can be added together. That is to say, afirst set of pixels using one pixel pattern and a second set of pixelsusing a different pattern can be added together. In this first case,there are essentially no common pixels between the two sets. In thesecond procedure, the second set of pixels can replace pixels of thefirst set. In this second case, there may be common pixels between thetwo sets.

In an embodiment, the first set of pixels 3102 and the second set ofpixels 3104 are non-overlapping pixels. In combining the first set ofpixels 3102 and the second set of pixels 3104 to form the image, thefirst set of pixels are added to the second set of pixels.

In another embodiment, the first set of pixels 3102 includes pixelscorresponding to the edge region 3108 of the ultrasonic sensor. Incombining the first set of pixels 3102 and the second set of pixels 3104to form the image, the pixels of the first set of pixels 3102corresponding to the edge region 3108 are replaced with the second setof pixels 3104 to form the image.

It is noted that in either case, it is possible that the edge region3108 may suffer some degradation from truncated beamforming.

FIG. 32 illustrates a flow diagram 3200 of an example method forgenerating an image, according to various embodiments. Procedures ofthis method will be described with reference to elements and/orcomponents of various figures described herein. It is appreciated thatin some embodiments, the procedures may be performed in a differentorder than described, that some of the described procedures may not beperformed, and/or that one or more additional procedures to thosedescribed may be performed. Flow diagram 3200 includes some proceduresthat, in various embodiments, are carried out by one or more processorsunder the control of computer-readable and computer-executableinstructions that are stored on non-transitory computer-readable storagemedia. It is further appreciated that one or more procedures describedin flow diagram 3200 may be implemented in hardware, or a combination ofhardware with firmware and/or software.

The degradation at the edges of a sub-block 3102, described above, maybe alleviated by the following method 3200 depicted in FIG. 32: first,capture 3205 a first set of pixels at an ultrasonic sensor using a firstbeamforming pattern, wherein the first beamforming pattern comprises afirst pattern of ultrasonic transducers of the ultrasonic sensor. Next,capture 3210 a second set of pixels at the ultrasonic sensor using asecond beamforming pattern, wherein the second beamforming patterncomprises a second pattern of ultrasonic transducers, wherein the secondbeamforming pattern is different than the first beamforming pattern, andwherein the second set of pixels corresponds to an edge region of theultrasonic sensor. Finally, combine 3210 the first set of pixels and thesecond set of pixels to form the image. While this method describes atwo-scan procedure, three scans may be employed, such as described inconnection with FIG. 34, discussed below.

It is possible to scan the edge pixels using an asymmetrical pattern.FIGS. 33A-33B illustrate the effects on edge pixels when scanning withan asymmetrical pattern, using a three-scan process to scan pixels 3302.(NOTE to patent attorneys: we need to re-write this section. Let's havea call). The first scan (not shown) is of an inner pixel pattern, suchas described above. The second scan is of the top and bottom edgepixels, where the bottom beam-forming pattern 3304′ is a mirror image ofthe top beam-forming pattern 3304. The third scan is of the left andright edge pixels, where the right beam-forming pattern 3306′ is amirror image of the left beam-forming pattern 3306.

The edge pixel beam-forming pattern achieves nearly the same Tx pressureand only slightly degraded resolution compared to the inner pixelbeam-forming pattern (spatial resolution ˜80 μm×˜100 μm versus ˜75μm×˜75 μm). The same method 3200 as described above may be employed hereas well, except that three scans (FIGS. 33A-33B), or even five scans(FIGS. 35A-35D) are used instead of two scans.

The final result 3400 is depicted in FIG. 34. The first set of pixels3402 obtained in the first scan is similar to the first set of pixels3102 above, using an inner pixel pattern. The second set of pixels 3404and the third set of pixels 3406 are obtained using second and thirdscans, respectively, of edge pixel patterns, as illustrated in FIGS.33A-33B.

FIGS. 35A-35D depict four of the five scans employed in a five-scanprocess to scan pixels 3502 in an imaged region 3504. The first scan(not shown) is of an inner pixel pattern, such as described above. Theremaining four scans are of edge pixel patterns, wherein FIG. 35A is ofthe top edge, using beam-forming pattern 3506, FIG. 35B is of the bottomedge, using beam-forming pattern 3508, FIG. 35C is of the left edge,using beam-forming pattern 3510, and FIG. 35D is of the right edge,using beam-forming pattern 3512. Some or all of the beam-formingpatterns 3506, 3508, 3510, and 3512 may or may not be the same patterns.The five scans are combined, as described above, to produce a resultsimilar to that obtain for FIG. 34.

In an embodiment related to the addition of the first set of pixels 3102and second set of pixels 3104 above, here, the method 3200 (FIG. 32) ofgenerating an image further includes capturing 3230 the third set ofpixels 3406 at the ultrasonic sensor using a third beamforming pattern.The third beamforming pattern comprises a third pattern of ultrasonictransducers. The third beamforming pattern is different than the firstbeamforming pattern and the second beamforming pattern. Additional setsof pixels (not shown) may also be captured to further generate theimage, using other beamforming pattern(s). Each additional beamformingpattern comprises a pattern of ultrasonic transducers that is differentthan the other beamforming patterns. For example, four scans, or evenfive scans, may be used to capture additional sets of pixels. Such scansmay involve an overall scan, such as described above, together with anumber of edge scans, either simultaneously or sequentially. In anembodiment of a five scan approach, the overall scan (e.g., symmetrical)may be taken, followed by a scan (e.g., asymmetrical) of each edgeseparately (top edge, bottom edge, left edge, and right edge, in anyorder), following essentially the same procedures as described above.

As above, there are two procedures that can be performed with capturedpixels. In the first procedure, pixels can be added together. That is tosay, all sets of pixels can be added together. In this first case, thereare essentially no common pixels between the several sets. In the secondprocedure, the second set of pixels can replace pixels of the first set.In this second case, there may be common pixels between the two sets.For instance, the second set of pixels can replace edge pixels of thefirst set (where they overlap) and the third set of pixels can be addedto the first set (where they do not overlap).

In one embodiment, the method 3200 further includes adding 3235 thefirst set of pixels 3402, the second set of pixels 3404, and the thirdset of pixels 3406 to form the image. The second pattern of ultrasonictransducers occupies a first edge pixel pattern 3408 and the thirdpattern of ultrasonic transducers occupies a second edge pixel pattern3410.

In another embodiment related to the replacement of the pixels of thefirst set of pixels 3102 corresponding to the edge region 3108 with thesecond set of pixels 3104 above, here the method 3200 further includesthe capturing 3230 procedure described above, but in combining thefirst, second, and third set of pixels, the first set of pixels 3402,the second set of pixels 3404, and the third set of pixels 3408 arecombined 3240 to form the image such that the second set of pixels andthird set of pixels replace edge pixels 3408 and 3410 of the first setof pixels 3402. The second pattern of ultrasonic transducers occupies afirst edge pixel pattern 3408 and the third pattern of ultrasonictransducers occupies a second edge pixel pattern 3410.

The phase delay described above in connection with FIGS. 14-19 and21-25B may be employed with the use of two beamforming patterns or threebeamforming patterns, as described above. Here, the beamforming patternsactivate different transducers with different signal delays, to focuseach beam to a single point on the ultrasonic sensor.

An electronic device 1300 comprises an ultrasonic sensor 1200, aprocessing logic module 1340, and a processor connected to theprocessing logic module and configured to perform the steps of combiningtwo beamforming patterns or three beamforming patterns, as describedabove.

A method of generating an image of a fingerprint uses the methoddescribed above. The fingerprint sensing system 1250 comprises anultrasonic sensor 1200 comprising a plurality of ultrasonic transducersto transmit a first ultrasonic beam from sets of pixels toward a surface1216 configured to receive a finger 1252 having the fingerprint thereonand to receive a second ultrasonic beam reflected from the fingerprint.The second ultrasonic beam generates a signal for processing in a signalprocessor 1240.

What has been described above includes examples of the subjectdisclosure. It is, of course, not possible to describe every conceivablecombination of components or methodologies for purposes of describingthe subject matter, but it is to be appreciated that many furthercombinations and permutations of the subject disclosure are possible.Accordingly, the claimed subject matter is intended to embrace all suchalterations, modifications, and variations that fall within the spiritand scope of the appended claims.

In particular and in regard to the various functions performed by theabove described components, devices, circuits, systems and the like, theterms (including a reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., a functional equivalent), even though not structurallyequivalent to the disclosed structure, which performs the function inthe herein illustrated exemplary aspects of the claimed subject matter.

The aforementioned systems and components have been described withrespect to interaction between several components. It can be appreciatedthat such systems and components can include those components orspecified sub-components, some of the specified components orsub-components, and/or additional components, and according to variouspermutations and combinations of the foregoing. Sub-components can alsobe implemented as components communicatively coupled to other componentsrather than included within parent components (hierarchical).Additionally, it should be noted that one or more components may becombined into a single component providing aggregate functionality ordivided into several separate sub-components. Any components describedherein may also interact with one or more other components notspecifically described herein.

In addition, while a particular feature of the subject innovation mayhave been disclosed with respect to only one of several implementations,such feature may be combined with one or more other features of theother implementations as may be desired and advantageous for any givenor particular application. Furthermore, to the extent that the terms“includes,” “including,” “has,” “contains,” variants thereof, and othersimilar words are used in either the detailed description or the claims,these terms are intended to be inclusive in a manner similar to the term“comprising” as an open transition word without precluding anyadditional or other elements.

Thus, the embodiments and examples set forth herein were presented inorder to best explain various selected embodiments of the presentinvention and its particular application and to thereby enable thoseskilled in the art to make and use embodiments of the invention.However, those skilled in the art will recognize that the foregoingdescription and examples have been presented for the purposes ofillustration and example only. The description as set forth is notintended to be exhaustive or to limit the embodiments of the inventionto the precise form disclosed.

What is claimed is:
 1. A method for generating an image, the methodcomprising: capturing a first set of image pixels by an ultrasonicsensor comprising an array of ultrasonic transducers using a firstbeamforming pattern, wherein the first beamforming pattern comprises afirst pattern of transmit signals routed to a plurality of ultrasonictransducers of the ultrasonic sensor, wherein the first beamformingpattern activates transducers with different signal delays, to focuseach beam to a single point over the ultrasonic sensor; capturing asecond set of image pixels by the ultrasonic sensor using a secondbeamforming pattern, wherein the second beamforming pattern comprises asecond pattern of transmit signals routed to the plurality of ultrasonictransducers, wherein the second beamforming pattern is different thanthe first beamforming pattern, wherein the second beamforming patternactivates different transducers with different signal delays, to focuseach beam to a single point over the ultrasonic sensor, and wherein thesecond set of image pixels corresponds to a different region of theultrasonic sensor than the first set of image pixels; and combining thefirst set of image pixels and the second set of image pixels to form theimage.
 2. The method of claim 1, wherein the first set of image pixelsand the second set of image pixels are non-overlapping pixels.
 3. Themethod of claim 2, wherein the combining the first set of image pixelsand the second set of image pixels to form the image comprises: addingthe first set of image pixels to the second set of image pixels to formthe image.
 4. The method of claim 3, wherein the method furthercomprises: capturing a third set of image pixels by the ultrasonicsensor using a third beamforming pattern, the third beamforming patterncomprising a third pattern of transmit signals routed to the pluralityof ultrasonic transducers, wherein the third beamforming pattern isdifferent than the first and second beamforming patterns; wherein themethod further comprises combining the first set of image pixels, thesecond set of image pixels, and the third set of image pixels to formthe image.
 5. The method of claim 4, wherein the method furthercomprises: capturing at least one additional set of image pixels by theultrasonic sensor using at least one additional beamforming pattern,each additional beamforming pattern comprising a pattern of transmitsignals routed to the plurality of ultrasonic transducers, wherein eachadditional beamforming pattern is different than the first, second, andthird beamforming patterns; wherein the method further comprisescombining the first set of image pixels, the second set of image pixels,the third set of image pixels and each additional set of image pixels toform the image.
 6. The method of claim 4, wherein the second pattern ofultrasonic transducers occupies a first pixel pattern and the thirdpattern of ultrasonic transducers occupies a second pixel pattern. 7.The method of claim 1, wherein the combining the first set of imagepixels and the second set of image pixels to form the image comprises:replacing pixels of the first set of image pixels corresponding to thedifferent region with the second set of image pixels to form the image.8. The method of claim 7, wherein the method further comprises:capturing a third set of image pixels by the ultrasonic sensor using athird beamforming pattern, the third beamforming pattern comprising athird pattern of ultrasonic transducers, wherein the third beamformingpattern is different than the first and second beamforming patterns;wherein the method further comprises combining the first set of imagepixels, the second set of image pixels, and the third set of imagepixels to form the image such that the second set of image pixels andthird set of image pixels replaces some pixels of the first set of imagepixels.
 9. The method of claim 1, wherein the ultrasonic sensorcomprises a number of blocks of ultrasonic transducers.
 10. The methodof claim 9, wherein pixels for the blocks of ultrasonic transducers arecaptured in parallel.
 11. An electronic device comprising: an ultrasonicsensor; a processing logic module; and a processor connected to theprocessing logic module and configured to perform the steps of:capturing a first set of image pixels by an ultrasonic sensor comprisingan array of ultrasonic transducers using a first beamforming pattern,wherein the first beamforming pattern comprises a first pattern oftransmit signals routed to a plurality of ultrasonic transducers of theultrasonic sensor, wherein the first beamforming pattern activatestransducers with different signal delays, to focus each beam to a singlepoint over the ultrasonic sensor, capturing a second set of image pixelsby the ultrasonic sensor using a second beamforming pattern, wherein thesecond beamforming pattern comprises a second pattern of transmitsignals routed to the plurality of ultrasonic transducers, wherein thesecond beamforming pattern is different than the first beamformingpattern, wherein the second beamforming pattern activates differenttransducers with different signal delays, to focus each beam to a singlepoint over the ultrasonic sensor, and wherein the second set of imagepixels corresponds to a different region of the ultrasonic sensor thanthe first set of image pixels, and combining the first set of imagepixels and the second set of image pixels to form an image.
 12. Theelectronic device of claim 11, wherein the first set of image pixels andthe second set of image pixels are non-overlapping pixels.
 13. Theelectronic device of claim 11, wherein the ultrasonic sensor comprises anumber of blocks of ultrasonic transducers.
 14. The electronic device ofclaim 13, wherein image pixels for the blocks of ultrasonic transducersare captured in parallel.
 15. The electronic device of claim 11, whereinbeamforming patterns activate different transducers with differentsignal delays, to focus each beam to a single point on the ultrasonicsensor.
 16. A method of generating an image of a fingerprint with afingerprint sensor comprising an ultrasonic sensor comprising aplurality of ultrasonic transducers to transmit a first ultrasonic beamfrom sets of ultrasonic transducers toward a surface configured toreceive a finger having the fingerprint thereon and to receive a secondultrasonic beam reflected from the fingerprint, the second ultrasonicbeam to generate a signal for processing in a signal processor, themethod comprising: capturing a first set of image pixels by anultrasonic sensor comprising an array of ultrasonic transducers using afirst beamforming pattern, wherein the first beamforming patterncomprises a first pattern of transmit signals routed to a plurality ofultrasonic transducers of the ultrasonic sensor; capturing a second setof image pixels by the ultrasonic sensor using a second beamformingpattern, wherein the second beamforming pattern comprises a secondpattern of transmit signals routed to the plurality of ultrasonictransducers, wherein the second beamforming pattern is different thanthe first beamforming pattern, and wherein the second set of imagepixels corresponds to a different region of the ultrasonic sensor thanthe first set of image pixels; and combining the first set of imagepixels and the second set of image pixels to form the image.
 17. Themethod of claim 16, wherein the first set of image pixels and the secondset of image pixels are non-overlapping pixels.
 18. The method of claim17, wherein the combining the first set of image pixels and the secondset of image pixels to form the image comprises: adding the first set ofimage pixels to the second set of image pixels to form the image. 19.The method of claim 16, wherein the combining the first set of imagepixels and the second set of image pixels to form the image comprises:replacing pixels of the first set of image pixels corresponding to thedifferent region with the second set of image pixels to form the image.20. The method of claim 16, wherein the method further comprises:capturing a third set of image pixels by the ultrasonic sensor using athird beamforming pattern, the third beamforming pattern comprising athird pattern of transmit signals routed to the plurality of ultrasonictransducers, wherein the third beamforming pattern is different than thefirst and second beamforming patterns; wherein the method furthercomprises combining the first set of image pixels, the second set ofimage pixels, and the third set of image pixels to form the image suchthat the second set of image pixels and third set of image pixelsreplaces some pixels of the first set of image pixels.